90 WHITEAVES ON THE OETHOCERATl DyE OE THE TEENTON, Etc. 



PLATE IX. 



AciiNocERAs EicuAEDSONi. (Page 83.) 



Fig. 1. — Exterior of a specimen from Lower Fort Garry, to shew the general shape and surface ornamentation. 



2. — Longitudinal section of another spjciman, from St. Andrews, Manitoba, to shew the characters of the 

 siphuncle and septa. 



2a.— Outline of transverse section of the same, at S. The dotted line in this figure shews whore the longi- 

 tudinal section represented in fig. 2 was made. 



3.— Posterior and apical end of a specimen from East Sslkirk, supposed to hi an abnormally flattened examp'e 

 of this species, a part of which has been cut longitudinally, to show the siphuncle and septa. 



3a.— Outline of transverse section of the same, to shew the relative proportions and position of the siphuncle 

 and endosiphon. 



PLATE X. 



Sactoceras Canadense. (Page 85.) 



Fig. \. — Exterior view of the only specimen in the Survey collection, which is a cast of the interior of the shell. 



la.— Another view of the same specimen, with most of the septate portion cut longitudinally, to shew the 



large size of the siphuncle posteriorly and its extreme diminution anteriorly. 

 lb. — Outline of transverse section of the same, at S 1. 

 le.— " " " " " " " at S 2. 



AcTI^ocERAS BiGSBYi. (Page 84.) 



Fig. 2.— Longitudinal .section of a specimen from Black Island, in which the apical extremity is preserved, shew- 

 ing the opening of the large foramen into the endosiphon posteriorly and some of the lateral canals or 

 tubuli which radiate outward and forward from the endosiphon. 



AcriNOGERAS Allumettense. (Page 85.) 



Fig. 3. — Longitudinal section of the only specimen known to the writer from the Trenton limestone of INIanitoba, 

 to shew the characters of both siplmncle and septa. 

 3a.— Outline of transverse section of the same, at S. The dotted lines indicate the place where the longi- 

 tudinal section was made. 



PLATE XL 



G0JJ10CBHA.S Lambii. (Page 80.) 



Fig. 1.— Antisiphonal and presumably dorsal side of the only specimen in tlie Survey collection, one-half the 

 natural size. 



la.— Siphonal and presumably ventral side of the same, partly cut longitudinally, to shew the characters of 

 the siphuncle and septa. One-lialf the natural size. 



lb. — Outline of transverse section of the same, at S. The dotted lines indicate the place where the longi- 

 tudinal section seen in fig. la was made. 



POTBEIOCERAS APERTUM. (Page 87.) 



Fig. 2. — Specimen which has been slightly worn down on the siphonal side, shewing the septa, part of the siph- 

 uncle, and the sudden inbending of the test at the aperture. 

 3.— Aperture of another specimen, as seen in a natural and longitudinal section nearer the centre, aud shew- 

 ing the sudden imbending and thickening of the test, as described also on page 87. 



POTBEIOCBRAS GRACILE. (Page 87-) 



j-jg. 4. — Lateral view of the type specimen of this species. The dotted lines indicate the place where the piece was 

 cut out, as represented in the next figure. 

 4a. — Siphonal and presumably ventral view of the same, with a piece cut out of the anterior end of the sep- 

 tate portion, to shew the position and character of the siphuncle. 

 4b. — Outline of transverse section of the same specimen, at S. 



